1889.] MR. W. K. PARKER ON STEATORNIS CARIPENSIS. 177 
the 13th sacral is identified as such by its close union (ankylosis) 
with the postero-superior angles of the post-ilia; its centrum is 
distinct from that of the 12th. 
Here, in this manifestly archaic bird we have, as in the Parrot 
tribe, a marvellous variety in the articulations and functions of the 
vertebral centra. 
The aélas is proccelous, and its joint, behind, with the azis, 
is flat, with a joint-cavity. The joint-cavity, with a perforated 
meniscus and a suspensory ligament, is seen up to the sacrum; but 
the cervicals, only, are cylindroidal; the dorsals are opisthoccelous. 
Then the sacrals are ankylosed, and behind these come the caudals ; 
which, in front, are subconcave on both faces, and are united by 
fibro-cartilage without a joint-cavity ; whilst in the hinder part of 
the series that cavity reappears in a proccelous joint. 
IV. The Sternum and Shoulder-girdle. 
The s¢ernum (Plate XVIII. figs. 7, 8) belongs to the same type 
as that of Caprimulgus on the one hand, and Buceros on the other, 
but is most like that of the latter. Like the pelvis it is short and 
broad, and it has only two notches; they are wide and rounded, 
and the xiphoids are all three finished behind by a large rounded 
plate of cartilage. _The whole structure is light and rather feeble, 
and the bone is pneumatic. The coracoid grooves nearly meet ; they 
form together little more than a right angle ; between them there is a 
short, blunt, inferior rostrum (7.st.), scooped above and carinate below. 
Together, the pre-costal process (pe.p.) and the costal edge form a 
high, nearly equilateral triangle ; there are four transverse condyles for 
the sternal ribs; the first of these only leaves a pre-costal tract 3°5 
millim. in extent. The body of the bone is deep and the keel large, 
with its fore margin at a right angle with the body; in front, the 
keel projects a little at its lower third, where the lesser pectoral muscle 
ends behind; it ends 4 millim. in front of the ossified part, and 
about 13 millim. from the end of the middle metasternal cartilage 
(middle xiphoid). The whole structure, shoulder-girdle and ster- 
num, is much like that of the Barn-Owl (Strix flammea), with its 
single notch right and left behind, the inner notches being nearly 
obsolete; that bird also has similar long scapule and coracoids, 
and the furcula are not unlike. 
This peculiar isomorphism with the Owl is manifestly adaptive ; 
I question if this bird is nearer akin to an Ow/ than it is to a Cor- 
morant. 
The structure of the sternum is in great contrast to that of the 
Common Goatsucker; in respect of its general finish it is more 
archaic. The comparative measurements are as follows :— 
Axial Breadth Breadth Length Depth 
length. infront. behind. ofkeel. of keel. 
millim. millim, millim, millim. millim. 
Caprimulgus.. 27 16 25 32 12 
Steatornis .. 58 43 52 45 18 
The notches in S¢eatornis measure 9 millim. axially and 15 
